Hi Guys,

I work for a company called Innovative Circuit Technology LTD., and we are an established manufacturer of general and industrial use power supplies, power conversion and charging products. The bulk of our offerings are available to view at www.ICT-Power.com or http://www.ictcorporate.com.

We have recently looked at diversifying into alternate markets due to internal interest from some of our design and sales staff, and one we’ve all agreed on is the hobby charging market, and more specifically, charging Lipo batteries. As it stands right now we have a working charger that is moving through the prototyping phase, but as I took a look at the market research I was surprised to see that we had previously perhaps overlooked some of the features end users may want. The things we’ve included to this point are as follows:

- Graphical White Backlit LCD ( 128x64 )
- 1mA Charge current steps
- The ability to charge up to an 8 cell pack
- USB output with PC software that can program new charge profiles, load included profiles ( 10 at this time ) and store graphical data
- Rotary Encoder for menu selection, and perhaps 1-2 other buttons
- Charge(8A)/Discharge (3A)/Storage Charge (50%)/Cycle
- Temperature Sensor
- Fan Cooling
- Dynamic graphing, so you can view extremely detailed sections of a charge, or see the entire graph profile in lesser detail


Reading through various forums I’ve noticed a trend toward end users actually modifying multi-cell LiPo packs to be able to charge the individual cells to more precise voltage levels. As we are still in the design phase, I want to get an idea of whether a charger that has multiple outputs is of great interest or not. We are looking at leaving our main output able to charge up to an 8 cell standard pack, but also adding 1-5 depending on size restraints and costs, individual outputs capable of only charging a 1-2 cell pack. This would give our unit the ability to charge not only the person who buys an 8 cell pack and wants a good efficient and effective charge, but also the enthusiast who wants to modify his pack and charge the cells individually, without having to buy multiple chargers. The limitation would be the additional outputs would only be able to do 1 or at most 2 cells at a time, so you couldn’t hookup 5, 4 cell lipo packs to the unit. We are trying to release a product into a market where there are established manufacturers already, but as our namesake indicates, we’d also like to try and be able to give a charger that has some features not readily available yet.

Any thoughts on what you’d be willing to sacrifice in terms of size and cost to achieve something like this, and any features that are overlooked in not only our prototype, but current production chargers is greatly appreciated. Other forums for us to work with would also be good points.

Ryan Kennedy
ICT, Engineering

http://img394.imageshack.us/img394/3306/ictlcd4at.th.jpg (http://img394.imageshack.us/my.php?image=ictlcd4at.jpg)

I personally feel that one great feature then most (all?) chargers on the market today is missing is a high quality charger that is able to charge more then one pack at a time, be it a 2-cell or 3-cell pack. While some aircraft guys use more then 3-cells, the vast majority (all?) car/truck guys use 2 or 3 cell packs.

I also think that a higher discharger rate (10A minimum) would be more useful then just 3A. I really like the idea of being able to download to a PC the charging data and hopefully discharge data would also be able to be downloaded.

Now I come from mainly a NiCd/NiMh background and if you want some ideas on what I feel would be a great charger/discharger for those I have tons of ideas :)

8 amp charge rate for less than $100 will be a winner!

Good input. The cost is something that will be determined near the end, depending on acutal build costs, and the feature set it ends up with.

As for charging mutiple packs, we are looking at mutliple outputs, and right now are focused on a single 8A output, and perhaps mulitiple 1-2A outputs, but perhaps two 5/6A outputs, both capable out charging up to 6 cell packs is a good idea as well. Across the forums I have noticed people have asked for this as most hae multiple packs, even when starting out, and would like to be able to charge them quickly ( ie more than one at once. ).

The discharge current is only limited by heat, and even at 3A it runs quite hot, especially if we want to size our case like out competitors. This may be adjusted, but a 10A discharge rate would create very high heat, requiring a much larger and more expensive fan/cooling solution.

Thanks,
Ryan
ICT, Engineering

The DuraTrax ICE has a 10amp discharge rate and is a very small unit (5.5" x 6" x 2"). It also charges both NiMh and LiPo packs but only has a single output. The same feature set with multiple outputs would be sweet. You can see the ICE at http://duratrax.com/caraccys/dtxp4170.html

No real need to discharge li-pos unless testing them. In that case 300 or more watts discharge may be nesseray, best to have a seperate component.

why would you disscharge a lipo? And what kind of battery are you going to charge at 8?


Brandon

Only in testing them would I discharge one or maybe to slightly balance the pack, Lipo's (big ones) can charge at 8 amps.

No real need to discharge li-pos unless testing them.

Really? Is this just what you have heard or have you actually testing them by cycling them at high amp rates? Not trying to be smart here but I hear the same thing but have never seen anyone that has actually done any real world testing to see if there is a difference.

We know that NiMh cells like to be discharged at high amp rates and we know that LiPo cells are different. But maybe they too like high discharge rates, maybe even higher then in normal use or maybe even a cycle of low amp discharge after use would make them better. LiPo's are so new I don't think anyone really knows and I would hate to buy a charger now that would need to be replaced in 6 months when someone finds out that a 30 amp discharge (or cycle) before storing is the ticket to get the most performance out of a pack.

All RC NiCd and NiMh cells have some type of conditioning that gives them the best performance. To think it is any different with LiPo's would be foolish.

I think that the opposite is true, with every discharge one life is spent. The lower the discharge rate the longer the cell will last. High discharge rates, high charge rates and high voltage charge termination and low voltage discharge termination just wastes the batteries.

You have intrigued me however to do some research on "cycling" li-pos. The only maintainence I know of benefit is to balance the packs. (which can be done by dischargeing a cell to match it with the other series cells.

I keep reading here about the LiPo cells and how much charge they hold. How stable have they become for use in a RC (trucks in my case). What kind of loss happens in a cycle with a LiPo cell, how many cycles will they run before there is significant falloff?

We just got that ICE unit in for testing, so we'll be able to verify all of the claims they make. Just looking at the case size and cooling solution, discharging at 10A on this unit will probably generate quite alot of heat.

The information out there on LiPo lifespan in terms of cycles, points towards them have much fewer full charge/discharge cycles in them than Li-Ion batteries. For this reason, I don't see very many people wasting many of these potentially valuable cycles discharging the cells very often, but there will be a portion that do, and if we didn't include discharging capabilities it would definitly hurt our product. This is strictly a LiPo charger right now, so the higher discharge rates needed for other battery types isn't being considered.

This is all still very speculative, as no one seems to have done repeated testing to see in fact if the number of cycles is in fact significantly lower than NiMH or Li-Ion.

Thanks,

Ryan Kennedy
ICT, Engineering

I think we have our hands full just trying to prevent fires with li-pos. I have verified the ice will discharge and charge according to it's specs. 1-20 volts. It will do 10 amps discharge and a 8 amp charge. The exception is it is a 120 watt max on the charge. with the exception of the impulse charge in which case will spike over 180 watts intermittently. All testing was on round cells though.

I am no expert on li-po and your charger specs I don't fully understand, but it seems the two main problems with li-po chargeing are the user overchargeing or over dischargeing. This has been addresed by "others" by aparrently using a built in lcv and a cell balanceing during charge. "They" are also using a 3c charge rate.

what is the mah on the batts you are charging at 8?



Brandon

I own a ICE charger and it is very nice. They use a couple of fans to keep the temps down and while it does get warm, it is not bad at all. If you are building a LiPo charger it should only take some additional programing to allow it to charge NiMh packs. Not being able to charge them I would think would greatly limit its market.

Taking the ICE's features and adding the capability to charge two packs at once would be a target to shoot for I would think. The ICE has a street price of $130 and that, I think, would be one of the most challaging features to beat.

I would agree, and add that a max voltage of 30 or so would've been nice too.

I was chargeing 3000 and 3300 mah nimh at 8 amps. The step charge and the zero-peak is very nice so far. I have been able to charge at far higher rates and yet still keep temps down.

what is your temp on the pack usually? and nimh is a lot diff then lipo. if you have say let's say a thunder power 3300 mah and charge it at 8 kiss that batt good buy! Not enless you have a temp probe?

Brandon

I was actually talking about the temp. of the ICE charger when discharing at 10 amps.

what is your temp on the pack usually? and nimh is a lot diff then lipo. if you have say let's say a thunder power 3300 mah and charge it at 8 kiss that batt good buy! Not enless you have a temp probe?

Brandon

Right now most are using a rate of 1C so a 8000 mah batt can charge at 8 amps

By the time I get into lipo we will be using 3C or more. FMA direct is claiming a 3c charge rate and 90% full. That is 20 minutes to charge. The claim is that with cell balance during charge they can use the high rate. I guess I don't understand why if they can use a 3c rate with cell balance then why is it not ok to use a 3c rate when doing just 1 cell?

I was actually talking about the temp. of the ICE charger when discharing at 10 amps.

You can lead a horse to water .......

Your right about the ICE Charger unit!!
Its does more then the $450.00 chargers.

Highly recommend using the thermal probe with the ICE charger!!! :thumbsup:

what is your temp on the pack usually? and nimh is a lot diff then lipo. if you have say let's say a thunder power 3300 mah and charge it at 8 kiss that batt good buy! Not enless you have a temp probe?

Brandon

My packs have been at 110-120 or about 30-40 over ambiant temps. This has been 10-20 degrees lower than my other chargers. I noticed this from day one with my ice. It is not just with the 4-step or zero-peak. It happened with a regular charge too. 2C rate on nimh.